The present invention relates to a computer program providing an interface for an industrial controller, and in particular, to a program providing a uniform interface to different software objects, possibly from different vendors.
Industrial controllers are special purpose computers used for the control of industrial processes and the like. While executing a stored control program, they read inputs from the control process and, for the logic of the control program, provide outputs to the control process. Such controllers differ from conventional computers in two major respects.
First, the architecture of the industrial controller is designed to allow it to be easily reconfigured to meet the demands of the particular process being controlled. Normally, therefore, the industrial controller is in modular form. The user selects different modules to be assembled together in a rack and linked together on a back plane in the rack. Varying numbers of inputs and outputs are accommodated with input/output (I/O) modules that may also fit in the rack or in a remote rack connected to the first rack over a control network.
The ability to modify the industrial controller to match the control process is furthered by writing custom program to be executed on the industrial controller. These programs may be both for the control of the industrial process and to provide human machine interfaces (HMIs), the latter which often depict a graphic representation of all or part of the process animated to show its current operating state. The use of custom written software makes in important to provide a simple yet powerful programming environment.
At times, it can be desirable to monitor or control an industrial process from a site that is remote from the industrial controller and the process itself. Such remote operations are well known, for example, using dedicated phone lines in proprietary communication protocols between the industrial controller and a remote HMI. With the development of the Internet and the World Wide Web, dedicated phone lines may be replaced within Internet-based communications between a remote program and a Web server communicating with or incorporated as part of the industrial controller. The promise of the Web is that any Internet connected computer can become a remote terminal for an industrial controller, or the industrial controller itself (when the Internet connected computer is loaded with the appropriate PC-Based Controller Software and Drivers).
Widespread use of Internet-based remote operation of industrial controllers is hampered by the need to carry specialized software for the remote computer allowing it to communicate with the industrial controller. Programs implementing, for example, complex graphical remote human machine interfaces, can be so large as to be cumbersome to transport and load onto the remote machine. Software maintenance of such dispersed remote programs, each of which may be customized to a particular industrial controller is extremely difficult.
In the parent application to the present application entitled “Internet Object Interface For Industrial Controller”, U.S. Ser. No. 09/904,929, assigned to the assignee of the present invention and hereby incorporated by reference, an object based interface is described in which the remote computer executes an applet that allows it to communicate with an interface server program. The interface server program allows the discovery, construction, and use of pre-existing software objects held at the industrial controller. The objects provide extremely small footprint to the remote program while simplifying the task of developing complex program.
The development of software objects for a human machine interface is a complex task, which could be prohibitively expensive in light of the size of the industrial control market. Ideally, therefore, it would be possible to use pre-existing objects developed for larger markets such as those related to general purpose programming languages such as COM, C++, Java, XML, or commercially available graphics packages. Selecting objects from only a single provider may offer a uniform programming environment, but result in a functionally limited set of objects. While these objects may be supplemented with objects from additional vendors, switching between object protocols of different vendors can be cumbersome. Further, using any proprietary object set carries with it the risk that the objects will be modified by the vendor or that the vendor will cease supporting particular objects or all objects. This lack of stability in the programming environment is undesirable in the area of industrial control where considerable cost is invested in the custom controller program.